Overview

Brief Summary

The soil-borne ascomycete Fusarium oxysporum is a pathogenic fungus common in soils around the world, and the cause of fusarium wilt, a deadly vascular wilting syndrome in plants.  Fusarium oxysporum comprises over 120 known strains or “special forms” (formae speciales; f. sp.), each of which is specific to a unique plant host in which it causes disease.  Collectively, these F. oxysporum strains infect and kill a large host range including many commercially harvested crops such as species in the Solenaceae family (tomatoes, peppers, potatoes, eggplant), watermelon, lettuce, legumes, beets, basil, strawberries, chrysanthemum, sugarcane, bananas, and multiple other species.  Fusarium oxysporum spores survive dormant in soil sometimes for 30 years, are easily spread in water, on machinery and seeds, and can hide in the rhizomes or vegetative cuttings of infected plants, showing no symptoms until transmitted to other individuals; all these are qualities that make this fungus an important and potentially devastating agricultural pest (Gonsalves and Ferreira 1993; Miller et al. 1996; New York Botanical Garden 2003; Wikipedia 2014a,b).

Of particular urgent threat currently is the Fusarium oxysporum f. sp. cubense; the special form specific to bananas, which causes Panama disease deadly to banana plants.  Cavendash bananas, the strain which compose 85% of world banana exports, are generally F. oxysporum-resistant, however fall susceptible to a new variant of F. oxysporum f.sp. cubense, termed Tropical Race 4 (Foc TR4).  FocTR4 was first identified in Asia in 1992, infecting the Philippines and Northern Australia shortly thereafter.  In 2013 Jordan and Mozambique reported TR4 infected crops creating intense concern for its inevitable spread into banana producing countries in Africa and South America.  Hygiene to reduce the spread of the fungus and transgenic techniques to introduce resistance genes into Cavendash bananas are tools researchers hope will save the industry (Butler 2013; IITA Press Release 2013; Plant Health Australia 2013; García-Bastidas et al. 2014; Wikipedia 2014c).

Fusarium oxysporum attacks its host by entering through the root.  It grows in the plant xylem, eventually blocking the vascular system.  This prevents transport of water and nutrients to the rest of the host, causing wilting, discoloration, and ultimately death of the plant (Gonsalves and Ferreira, 1993; Wikipedia 2014a).

In addition to having well-studied pathogenic activity in plants, the broad host range of Fusarium oxysporum extends outside plant kingdom, into Animalia.  It is an emerging opportunistic human pathogen, reported as one of the most common agents causing invasive fungal infections in immunocompromised patients; as F. oxysporum is resistant to most available antifungal drugs, these infections are serious and frequently fatal in mammals.  Scientists have proposed developing F. oxysporum as a universal model for understanding fungal virulence (Ortoneda et al. 2003). 

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Fusarium oxysporum Schlecht. as emended by Snyder and Hansen [1] comprises all the species, varieties and forms recognized by Wollenweber and Reinking [2] within an infrageneric grouping called section Elegans. While the species, as defined by Snyder and Hansen, has been widely accepted for more than 50 years [3][4], more recent work indicates this taxon is actually a genetically heterogeneous polytypic morphospecies [5][6] whose strains represent some of the most abundant and widespread microbes of the global soil microflora [7], although this last statement has not been proven or supported by actual data. These remarkably diverse and adaptable fungi have been found in soils ranging from the Sonoran Desert, to tropical and temperate forests, grasslands and soils of the tundra [8]. F. oxysporum strains are ubiquitous soil inhabitants that have the ability to exist as saprophytes, and degrade lignin [9][10] and complex carbohydrates [11][12][13] associated with soil debris. They are also pervasive plant endophytes that can colonize plant roots [14][15] and may even protect plants or be the basis of disease suppression [16][17.] Although the predominant role of these fungi in native soils may be as harmless or even beneficial plant endophytes or soil saprophytes, many strains within the F. oxysporum complex are pathogenic to plants, especially in agricultural settings.

Pathogenic strains of F. oxysporum have been studied for more than 100 years. The host range of these fungi is extremely broad, and includes animals, ranging from arthropods [18] to humans [19], as well as plants, including a range of both gymnosperms and angiosperms. While collectively, plant pathogenic F. oxysporum strains have a broad host range, individual isolates usually cause disease only on a narrow range of plant species. This observation has led to the idea of "special form" or forma speciales in F. oxysporum. Formae speciales have been defined as "...an informal rank in Classification.....used for parasitic fungi characterized from a physiological standpoint (e.g. by the ability to cause disease in particular hosts) but scarcely or not at all from a morphological standpoint. As a category, forma specialis is mentioned in, but not regulated by, the International Code of Botanical Nomenclature and sometimes it has been inconsistently applied. Exhaustive host range studies also have been conducted for relatively few formae speciales or F. oxysporum [20]. For more information on Fusarium oxysporum as a plant pathogen, see Fusarium wilt. Different strains of F. oxysporum have been used in the purpose of producing nanomaterials (especially Silver nanoparticles).

  • [10] Sutherland, J.B., Pometto, A.L. III and Crawford, D.L. 1983. Lignocellulose degradation by Fusarium species. Can. J. Bot. 61:1194-1198.
  • [11] Christakopoulos, P., Kekos, D., Macris, B.J., Claeyssens, M. and Bhat, M.K. 1995. Purification and mode of action of a low molecular mass endo-1,4-B-D-glucanase from Fusarium oxysporum. J. Biotechnol. 39:85-93.
  • [12] Christakopoulos, P., Nerinckx, W., Kekos, D., Macris, B. and Claeyssens, M. 1996. Purification and characterization of two low molecular mass alkaline xylanases from Fusarium oxysporum F3. J. Biotechnol. 51:181-180.
  • [13] Snyder, W.C. and Hansen, H.N. 1940. The species concept in Fusarium. Amer. J. Bot. 27:64-67.
  • [14] Gordon, T.R., Okamoto, D. and Jacobson, D.J. 1989. Colonization of muskmelon and nonsusceptible crops by Fusarium oxysporum f. sp. melonis and other species of Fusarium. Phytopathology 79:1095-1100.
  • [15] Katan, J. 1971. Symptomless carriers of the tomato Fusarium wilt pathogen. Phytopathology 61:1213-1217.
  • [16] Larkin, R.P., Hopkins, D.L. and Martin, F.N. 1993. Effect of successive watermelon plantings on Fusarium oxysporum and other microorganisms in soils suppressive and conducive to fusarium wilt of watermelon. Phytopathology 83:1097-1105.
  • [17] Lemanceau, P., Bakker, P.A.H.M., DeKogel, W.J., Alabouvette, C. and Schippers, B. 1993. Antagonistic effect of nonpathogenic Fusarium oxysporum Fo47 and pseudobactin 358 upon pathogen Fusarium oxysporum f. sp. dianthi. Appl. Environ. Microbiol. 59:74-82.
  • [18] Teetor-Barsch, G.H. and Roberts, D.W. 1983. Entomogenous Fusarium species. Mycopathologia 84:3-16.
  • [19 Nelson, P.E., Dignani, M.C. and Anaissie, E.J. 1994. Taxonomy, biology, and clinical aspects of Fusarium species. Clin. Microbiol. Rev. 7:479-504.
  • [1] Snyder, W.C. and Hansen, H.N. 1940. The species concept in Fusarium. Amer. J. Bot. 27:64-67.
  • [20] Kistler, H.C. 2001. Evolution of host specificity in Fusarium oxysporum. Pages 70-82 in: Fusarium: Paul E. Nelson Memorial Symposium. B.A. Summerell, J.F. Leslie, D. Backhouse, W.L. Bryden and L.W. Burgess, eds. The American Phytopathological Society, St. Paul, MN.
  • [2] Wollenweber, H.W. and Reinking, O.A. 1935. Die Fusarien, ihre Beschreibung, Schadwirkung und Bekampfung. P. Parey, Berlin. 365 pp.
  • [3] Booth, C. 1971. The Genus Fusarium. Commonwealth Mycological Institute, Kew, Surrey, UK, 237 pp.
  • [4] Nelson, P.E., Toussoun, T.A. and Marasas, W.F.O. 1983. Fusarium species: An illustrated manual for identification. Pennsylvania State University Press, University Park.
  • [5] O'Donnell, K. and Cigelnik, E. 1997. Two divergent intragenomic rDNA ITS2 types within a monophyletic lineage of the fungus Fusarium are nonorthologous. Mol. Phylogenet. Evol. 7:103-116.
  • [6] Waalwijk, C., De Koning, J.R.A., Baayen, R.P. and Gams, W. 1996. Discordant groupings of Fusarium spp. from section Elegans, Liseola and Dlaminia based on ribosomal ITS1 and ITS2 sequences. Mycologia 88:361-368.
  • [7] Gordon, T.R. and Martyn, R.D. 1997. The evolutionary biology of Fusarium oxysporum. Annu. Rev. Phytopathol. 35:111-128.
  • [8] Stoner, M.F. 1981. Ecology of Fusarium in noncultivated soils. Pages 276-286 in: Fusarium: Diseases, Biology, and Taxonomy. P.E. Nelson, T.A. Toussoun and R.J. Cook, eds. The Pennsylvania State University Press, University Park.
  • [9] Rodriguez, A., Perestelo, F., Carnicero, A., Regalado, V., Perez, R., De la Fuente, G. and Falcon, M.A.1996. Degradation of natural lignins and lignocellulosic substrates by soil-inhabiting fungi imperfecti. FEMS Microbiol. Ecol. 21:213-219.
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Comprehensive Description

General Description

 On Potato Sucrose Agar (PSA). Colonies. After 4 days growth of isolates ranges from 4.5-6.35 cm diam. with a mean ñ SD = 4.09 ñ 0.52; mycelium delicate white with purplish pink or grayish magenta or white with a purple pigmentation. On Potato Dextrose Agar (PDA). Colonies. After 10 days growth on slants ranges from 7-8.25 cm length with a mean ñ SD = 7.05 ñ 0.43; mycelium sparse or abundant ranging in colour from white to pale violet or violet white; small pale brown, blue or violet sclerotia sometimes produced abundantly; mycelium producing terminal or intercalary, smooth or rough walled "chlamydospores" abundantly and quickly, usually singly, in pairs, in clusters or in short chains. Conidia. Of two types; macroconidia sparse in some strains, but usually abundant in sporodochia, straight to slightly curved, thin walled, 27-60 × 3-5 μm, usually 3- to 5-septate, 3-septate being most common, each with a tapering and curved apical cell and foot shaped basal cell; microconidia abundant, oval, elliptical, straight to curved, usually 0-septate, 5-12 × 2-3.5 μ, produced in false heads on short monophialidic conidiogenous cells. Teleomorph. Not known. Notes. This species usually produces pale violet (Potato Dextrose Agar) or magenta (Potato Dextrose Agar) pigmentation; it grows on Glycerol Nitrate Agar (G25N) with white or pale yellow aerial mycelium and yellow pigmentation; growth on mannitol sucrose medium results in white or reddish white or red aerial mycelium and red or brownish red or grayish red pigmentation; growth on Czapek-Dox Iprodione Dichloran Agar (CZID) results in white or pinkish white or pink aerial mycelium and brownish grey or purplish grey pigmentation. The species produces urease and phosphatase enzymes, but does not produce acid on creatine sucrose agar and acetylmethylcarbinol compound. Different isolates vary in production of peroxidase and pyrocatechol oxidase enzymes. 
  •  Nafady, N.A. 2008. Ecological, physiological and taxonomical studies on the genus Fusarium in Egypt. MSc thesis, Faculty of Science, Assiut University, Egypt. 
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Distribution

 Argentina; Armenia; Australia (Australian Capital Territory, New South Wales, Northern Territory, Queensland, Victoria, Western Australia); Azerbaijan; Bangladesh; Belarus; Brazil (Distrito Federal, Pará, Paraíba, Pernambuco, Rio de Janeiro, Santa Catarina, São Paulo); Brunei; Bulgaria; Burkina Faso; Canada (Alberta, Ontario, Québec, Saskatchewan); Chile; China (Hong Kong); Colombia; Costa Rica; Cuba; Cyprus; Denmark; Dominica; Dominican Republic; Ecuador; Egypt; Ethiopia; former USSR; France; Georgia; Greece; Guyana; Honduras; India (Andhra Pradesh, Assam, Bihar, Gujarat, Jammu & Kashmir, Karnataka, Kerala, Madhya Pradesh, Maharashtra, Meghalaya, Mysore, Orissa, Punjab, Rajasthan, Tamil Nadu, Uttar Pradesh); Israel; Italy; Jamaica; Japan; Jordan; Kazakhstan (Kustanai oblast); Kenya; Kyrgyzstan; Latvia; Madagascar; Malawi; Malaysia; Mexico; Moldova; Namibia; New Zealand; Nigeria; Pakistan; Panama; Philippines; Poland; Portugal; Puerto Rico; Russia (Altaiskyi krai, Irkutskaya oblast, Kaluga oblast, Kamchatskaya oblast, Krasnodarskyi krai, Leningradskaya oblast, Moscow oblast, Nizhegorodskaya oblast, Primorskyi krai, Sakhalinskaya oblast, Saratovskaya oblast, Stavropol’skyi krai); Singapore; Solomon Islands; South Africa; Spain; Sri Lanka; St Lucia; Sudan; Switzerland; Taiwan; Tanzania; Thailand; Trinidad & Tobago; Uganda; UK; Ukraine; Uruguay; USA (Alabama, California, Florida, Hawaii, Maryland, Texas); Uzbekistan; Venezuela; Zaire; Zambia; Zimbabwe. 
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Ecology

Associations

Foodplant / pathogen
embedded, apothecium-bearing sclerotium of Fusarium oxysporum infects and damages stem of Gladiolus x hortulanus

Foodplant / pathogen
Fusarium oxysporum infects and damages stem of Matthiola incana

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Associated Organisms

 Abelmoschus esculentus; Acacia luderitzii; Acacia nebrownii; Acroptilion repens; Agapanthus africanus; Albizia sp.; Albizia julibrissin; Alliaria petiolata; Allium cepa; Allium sativum; Amaranthus sp.; Ananas comosus; Anemone sp.; Arabidopsis thaliana; Arachis hypogaea; Asparagus officinalis; Avena sp.; Avena sativa; Azadirachta indica; Azalea sp.; Bambusa nutans; Beta vulgaris; Bougainvillea sp.; Brassica sp.; Brassica carinata; Brassica juncea; Brassica napus; Brassica napus var. oleifera; Brassica nigra; Brassica oleracea; Brassica oleracea var. capitata; Brassica oleracea var. gongyloides; Brassica rapa; Cajanus cajan; Callistephus sp.; Callistephus chinensis; Capsicum sp.; Capsicum annuum; Capsicum frutescens; Carthamus tinctorius; Centrosema acutifolium; Chrysanthemum sp.; Cicer arietinum; Citrullus lanatus; Citrus sp.; Clematis sp.; Clitoria ternatea; Cocos nucifera; Coffea sp.; Coffea arabica; Coffea canephora; Coffea excelsa; Coffea stenophylla; Colias polyographus; Colocasia Schott.; Colophospermum mopane; Craspedia sp.; Crossandra sp.; Cucumis melo; Cucumis sativus; Cucurbita maxima; Cuminum cyminum; Curcuma longa; Cynara scolymus; Cyperus rotundus; Dahlia sp.; Dianthus sp.; Dianthus caryophyllus; Dioscorea sp.; Dioscorea rotundata; Dracaena sp.; Elaeis guineensis; Elettaria cardamomum; Eucalyptus sp.; Eucalyptus globulus; Eucalyptus gomphocephala; Eucalyptus grandis; Eucalyptus maculata; Eucalyptus pauciflora; Eucalyptus tereticornis; Festuca ciliata; Fragaria sp.; Fragaria ananassa; Fusarium flocciferum; Gerbera sp.; Gibberella avenacea; Gibberella intricans; Gladiolus sp.; Gladiolus hybridus C. Morr.; Gliocladium roseum; Gliocladium viride; Gossypium sp.; Gossypium hirsutum; Gramineae sp.; Gypsophila sp.; Hedychium coronarium; Heliothis helicoverpa; Heterodera rostochiensis; Hibiscus rosaesinensis; Homo sapiens; Hordeum sp.; Hymenoptera sp.; Hypothenemus hampei; Ilex aquifolium; Ipomoea batatas; Iris sp.; Lathyrus sativus; Lavandula angustifolia; Leguminosae sp.; Liliaceae sp.; Lotus corniculatus; Lupinus sp.; Lycopersicon sp.; Lycopersicon esculentum; Lymantria dispar; Magnoliopsida sp.; Malus pumila; Medicago sativa; Momordica charantia; Morus alba; Murraya koenigii; Musa sp.; Musa acuminata; Musa paradisiaca; Musa paradisiaca subsp. sapientum; Myrothecium verrucaria; Narcissus sp.; Nectria haematococca; Nematoda sp.; Nesiota elliptica; Nigella sativa; not identified; Ocimum basilicum; Orobanche sp.; Orobanche alsatica; Orobanche crenata; Orontium sp.; Oryza sp.; Oryza sativa; Panax ginseng; Panicum sp.; Passiflora edulis; Pelargonium graveolens; Phaseolus vulgaris; Phoenix sp.; Phoenix dactylifera; Phytolacca dioica; Pinus sp.; Pinus banksiana; Pinus caribaea; Pinus elliottii; Pinus halepensis; Pinus kesiya; Pinus lambertiana; Pinus nigra; Pinus oocarpa; Pinus patula; Pinus pinaster; Pinus pinea; Pinus radiata; Pinus resinosa; Pinus strobus; Pinus sylvestris; Piper nigrum; Pisum sativum; Plantae sp.; Plutella xylostella; Poncirus trifoliata; Populus sp.; Prunus amygdalus; Prunus armeniaca; Prunus avium; Prunus persica; Psidium guajava; Pterocarpus indicus; Pyrus sp.; Pyrus communis; Raphanus sativus; Ricinus communis; Rosa sp.; Saccharum officinarum; Schlumbergera sp.; Secale sp.; Secale cereale; Simmondsia chinensis; Sinapis alba; Solanum melongena; Solanum tuberosum; Spinacia oleracea; Striga hermontheca; Syngonium sp.; Taxus cuspidata; Theobroma cacao; Thlaspi arvense; Trifolium repens; Triticum sp.; Triticum aestivum; Triticum durum; Tulipa sp.; Vanilla sp.; Vicia faba; Vigna aconitifolia; Vigna cajanga; Vigna unguiculata; Vigna unguiculata subsp. sesquipedalis; Vitis vinifera; Voandzeia subterranea; Washingtonia filifera; Xanthosoma sp.; Xanthosoma sagittifolium; Zantedeschia aethiopica; Zea mays; Zingiber officinale; Zinnia sp. 
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Molecular Biology and Genetics

Molecular Biology

Barcode data: Fusarium oxysporum

The following is a representative barcode sequence, the centroid of all available sequences for this species.


There is 1 barcode sequence available from BOLD and GenBank.

Below is the sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.

See the BOLD taxonomy browser for more complete information about this specimen.

Other sequences that do not yet meet barcode criteria may also be available.

TATTTAATATTCGCTCTTTTCTCTGGATTATTAGGTACAGCTTTTTCAGTGTTAATTAGACTTGAACTTAGTGGGCCAGGAGTTCAATATATTTCTAATAA---TCAATTATATAACAGTGTAATTACAGCTCACGCTATATTAATGATATTCTTCATG---GTTATGCCAGCATTAATAGGTGGGTTTGGAAATTTTTTAATGCCTTTAATGGTAGGTGGTCCGGATATGGCATTCCCTAGATTAAATAATATAAGTTTCTGATTATTACCTCCTAGTTTAATATTATTGGTATTTTCAGCCATAATTGAAGGTGGAGTGGGTACAGGT------------TGAACACTTTATCCCCCATTATCAGGATTACAAAGTCATAGTGGACCTAGTGTAGATCTTGCTATTTTTACTTTACATTTAACAGGGGTAAGTAGTTTATTAGGATCGATAAATTTTATAACAACAATTGTAAATATGAGAACGCCAGGAATAAGATTACATAAATTAGCATTATTCGGATGAGCAGTAGTTATAACAGCAGTATTACTTTTATTATCATTACCTGTATTAGCTGGTGGTATAACTATGGTGTTAACAGATAGAAATTTTAATACATCATTCTTTGAAGTAGCAGGTGGAGGAGATCCTATATTATTCCAACATCTT
-- end --

Download FASTA File

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Statistics of barcoding coverage: Fusarium oxysporum

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 1
Specimens with Barcodes: 1
Species With Barcodes: 1
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Wikipedia

Koa wilt


Koa Wilt is a relatively new disease to Hawaii, discovered in 1980. Koa Wilt is caused by the fungus Fusarium oxysporum, which is now abundant in Hawaiian soils and infects the native Acacia koa tree, a once-dominant species in the canopy of Hawaiian forests. F. oxysporum f.sp. koae is believed to have been brought into Hawaii on an ornamental acacia plant.[1] Fusarium fungi clog the tree xylem, causing significant wilt and mortality among these beautiful and iconic Hawaiian trees.

Hosts and Symptoms[edit]

Upper branches of a healthy koa tree, showing the bark, sickle-shaped phyllodes, greenish rounded flower heads, and seedpods

The host for Koa Wilt is Acacia koa, a tree that is native and endemic to the Hawaiian islands. It ranges in size from 15 to greater than 50 feet [2] with a canopy spread of 20 to 40 feet.[3] It has a showy white flower and blooms sporadically. Mature leaves are sickle shaped.[4]

Koa wilt is typically a fatal pathogen for its host. In only a few months, a tree may lose its entire canopy and die. Trees less than fifteen years old are typically the most susceptible. Symptoms include stains in cambium, roots, and sapwood as well as chlorosis (yellowing), canopy dieback, brown and wilted leaves, oozing sap, and bark cankers.[5]

Disease Cycle[edit]

The Koa Wilt pathogen was first described by Gardner as a new forma specialis, Fusarium oxysporum. f. sp. koae.[6] The soil-borne F. oxysporum reproduces only asexually. F. oxysporum produces three types of asexual spores: microconidia, macroconidia, and chlamydospores. Microconidia are the spore types most often produced by this fungus under all conditions, as well as the spores produced in the xylem. The macroconidia are found on dead plant tissue surfaces as well as in groups that look like sporodochia. The chlamydospores are round, resting spores, produced on older mycelium or in macroconidia. Mycelium enters the roots and travels into the vascular xylem where it starts to produce microconidia, eventually clogging the xylem. Once the Koa tree dies, the fungus invades all tissues and, upon reaching the dead plant surface, sporulates profusely producing macroconidia and chlamydospores. The fungus can survive saprophytically in the soil, as either mycelium or as any of its three spore types mentioned. The chlamydospores, as the resting spores, survive the longest in the soils, usually under cold conditions.[7]

Environment[edit]

Koa trees occupy dry to mesic areas on the islands of Kauaʻi, Oʻahu, Molokaʻi, Lānaʻi, Maui, and Hawaiʻi in elevations of 80 to 8,000 feet with 0 to 100 inches of rain. They are a dominant forest species. Koa wilt has been found on the islands of Kauaʻi, Oʻahu, Maui, and Hawaiʻi. Most diseased trees are found at elevations below 3,000 feet.[8] However, it has also been observed at elevations as high as 7,000 feet.[9] Fusarium, the primary cause of Koa Wilt, May be found in a variety of environments but thrives with the high temperatures and moist soils of Hawaii. It survives in the soil.[10]

Management[edit]

F. oxysporum is a soil-borne pathogen, and currently sanitation, controlling the initial inoculum, is the best means to control it. One should avoid bringing infected soil or plant tissues into disease free areas. Make certain that all tools and equipment have been cleaned and sterilized after contact with infected sites and plants. New plantings should be in areas known to be free of the pathogen, and the soils should be screened to ensure that no F. oxysporum is present. Seeds are not usually infected, but there is a slight risk and therefore only seeds that are from local, clean, superior trees should be used.[11] Seedlings should be started in soil-less media, although there is still a risk of wind-borne pathogen contamination.[12] When planting in areas where there are no local hosts, it is suggested that one plant seeds from several different sources in the hope of finding a resistant tree.[13] Currently, research about Koa Wilt is focused primarily on determining resistant Koa varieties.

Importance[edit]

Koa is a commodity, a dominant native forest species, and an important element of Hawaiian culture. Koa is highly-prized hardwood that can sell for prices as high as $150 a board foot, a special measurement indicating one-foot by one-foot by one-inch wood piece.[14] Koa is currently being grown on plantations to support this high demand, yet some plantations have a 90% tree mortality rate over several years due to Koa Wilt.[15] It is also a legume, giving it the ability to form symbiosis with nitrogen fixing bacteria, which has led to efforts to use koa in agroecological systems with crops such as coffee and cacao.

Ecologically, koa is an important species because it is one of the few native trees that remains dominant in alien mixed forests on the Hawaiian Islands. Invasive species make up the majority of the State's current plant population. Koa trees also are important because provide a habitat for many native bird species. Historically, there were once two species of koa-finches, Rhodacanthis palmeri and R. flaviceps, which fed on green koa seed pods. These species are now extinct due to habitat loss and avian malaria.[16] It is important to preserve the remaining koa populations to helpt to avoid further native bird extinctions.

Koa also has great cultural importance for native Hawaiians. The name “koa” means "brave, bold, fearless" or "warrior" in Hawaiian. Koa wood was used extensively in ancient Hawaiian society for constructing houses, spears, tools, canoe paddles, kahili (feathered standards of royalty), calabashes, ceremonies, and surfboards.[17] Canoes were, and still are, carved from the trunks of koa trees. Outrigger canoe racing, often in koa canoes, is still a popular and highly competitive sport of cultural significance.

References[edit]

  1. ^ Friday, J. B., and Nicholas Dudley. "Hawai'i Forestry Extension: Koa Wilt." Hawai'i Forestry Extension: Koa Wilt. University of Hawaii, 31 Mar. 2013. Web. 23 Oct. 2014.
  2. ^ University of Hawaii. "Acacia Koa." Native Plants Hawaii. University of Hawaii, 2009. Web. 23 Oct. 2014
  3. ^ Elevitch, Craig R., Isabella Aiona. Abbott, and Roger R. B. Leakey. Traditional Trees of Pacific Islands: Their Culture, Environment, and Use. Hōlualoa, Hawaiʻi: Permanent Agriculture Resources, 2006. Print.
  4. ^ University of Hawaii. "Acacia Koa." Native Plants Hawaii. University of Hawaii, 2009. Web. 23 Oct. 2014
  5. ^ Friday, J. B., and Nicholas Dudley. "Hawai'i Forestry Extension: Koa Wilt." Hawai'i Forestry Extension: Koa Wilt. University of Hawaii, 31 Mar. 2013. Web. 23 Oct. 2014.
  6. ^ Gardner, D.E. 1980. Aciaca Koa Seedling Wilt Caused by Fusarium Oxysporum Phytopathology 70:594-597
  7. ^ Agrios, George 2005. Plant Pathology. Elsevier Academic Press, Burlington, MA.
  8. ^ Friday, J. B., and Nicholas Dudley. "Hawai'i Forestry Extension: Koa Wilt." Hawai'i Forestry Extension: Koa Wilt. University of Hawaii, 31 Mar. 2013. Web. 23 Oct. 2014.
  9. ^ Anderson, R.C., D.E. Gardner, C.C. Daehler, and F.C. Meinzer. 2002. Dieback of Acacia koa in Hawaii: ecological and pathological characteristics of affected stands. For. Ecol. and Mgmt.
  10. ^ Agrios, George 2005. Plant Pathology. Elsevier Academic Press, Burlington, MA.
  11. ^ Friday, J. B., and Nicholas Dudley. "Hawai'i Forestry Extension: Koa Wilt." Hawai'i Forestry Extension: Koa Wilt. University of Hawaii, 31 Mar. 2013. Web. 23 Oct. 2014.
  12. ^ Dudley, N., R.L. James, R.A. Sniezko, and A. Yeh. 2007. Pathogenicty of Four Fusarium Species on Acacia Koa Seedlings. Forest Health Protetion Numbered Report 07-04, USDA Forest Service Northern Region, Missoula, Montana.
  13. ^ Friday, J. B., and Nicholas Dudley. "Hawai'i Forestry Extension: Koa Wilt." Hawai'i Forestry Extension: Koa Wilt. University of Hawaii, 31 Mar. 2013. Web. 23 Oct. 2014.
  14. ^ Woodshop News. "Koa Is Highly Sought and High-priced." Woodshop News. Woodshop News, 9 Mar. 2009. Web. 23 Oct. 2014.
  15. ^ Friday, J. B., and Nicholas Dudley. "Hawai'i Forestry Extension: Koa Wilt." Hawai'i Forestry Extension: Koa Wilt. University of Hawaii, 31 Mar. 2013. Web. 23 Oct. 2014.
  16. ^ University of Hawaii. "Acacia Koa." Native Plants Hawaii. University of Hawaii, 2009. Web. 23 Oct. 2014.
  17. ^ University of Hawaii. "Acacia Koa." Native Plants Hawaii. University of Hawaii, 2009. Web. 23 Oct. 2014.
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Fusarium oxysporum

The ascomycete fungus Fusarium oxysporum Schlecht. as emended by Snyder and Hansen[1] comprises all the species, varieties and forms recognized by Wollenweber and Reinking[2] within an infrageneric grouping called section Elegans. While the species, as defined by Snyder and Hansen, has been widely accepted for more than 50 years,[3][4] more recent work indicates this taxon is actually a genetically heterogeneous polytypic morphospecies[5][6] whose strains represent some of the most abundant and widespread microbes of the global soil microflora,[7] although this last statement has not been proven or supported by actual data. These remarkably diverse and adaptable fungi have been found in soils ranging from the Sonoran Desert, to tropical and temperate forests, grasslands and soils of the tundra.[8] F. oxysporum strains are ubiquitous soil inhabitants that have the ability to exist as saprophytes, and degrade lignin[9][10] and complex carbohydrates[11][12][13] associated with soil debris. They are also pervasive plant endophytes that can colonize plant roots[14][15] and may even protect plants or be the basis of disease suppression.[16][17] Although the predominant role of these fungi in native soils may be as harmless or even beneficial plant endophytes or soil saprophytes, many strains within the F. oxysporum complex are pathogenic to plants, especially in agricultural settings.

Because the hosts of a given forma specialis usually are closely related, many have assumed that members of a forma specialis are also closely related and have came about by descent from common ancestor. [18] However, results from recent research conducted on *Fusarium oxysporum f.sp. cubense have forced scientists to question these assumptions. Researchers used anonymous, single-copy restriction fragment length polymorphsims (RFLPs) to identify 10 clonal lineages from a collection of F. oxysporum f. sp. cubense from all over the world. These results showed that pathogens of banana could be closely related to other host’s pathogens, such as melon or tomato, as they are to each other. Exceptional amounts of genetic diversity within F. oxysporum f. sp. cubense also have been deduced from the high level of chromosomal polymorphisms found among strains, random amplified polymorphic DNA fingerprints, and from the number and geographic distribution of vegetative compatibility groups. [19]

Presented with the wide-ranging occurrence of F. oxysporum strains that are nonpathogenic, it is reasonable to expect that certain pathogenic forms were descended from originally nonpathogenic ancestors. Given the association of these fungi with plant roots, a form that is able to grow beyond the cortex and into the xylem could quickly take advantage of this ability and hopefully gain an advantage over those fungi that are restricted to the cortex. The progression of a fungus into the vascular tissue may elicit a response from the host immediately, successfully restricting the invader; or an otherwise ineffective or delayed response, reducing the vital water-conducing capacity to induce wilting. [20] On the other hand, the plant might be able to tolerate limited growth of the fungus within xylem vessels, preceded by an endophytic association.[21]In this case, any further changes in the host or parasite could disturb the relationship, in a way that fungal activities or a response of the host would result in the generation of certain disease symptoms.

Pathogenic strains of F. oxysporum have been studied for more than 100 years. The host range of these fungi is extremely broad, and includes animals, ranging from arthropods[22] to humans,[23] as well as plants, including a range of both gymnosperms and angiosperms. While collectively, plant pathogenic F. oxysporum strains have a broad host range, individual isolates usually cause disease only on a narrow range of plant species. This observation has led to the idea of "special form" or forma specialis in F. oxysporum. Formae speciales have been defined as "...an informal rank in Classification.....used for parasitic fungi characterized from a physiological standpoint (e.g. by the ability to cause disease in particular hosts) but scarcely or not at all from a morphological standpoint." Exhaustive host range studies have been conducted for relatively few formae speciales of F. oxysporum.[24] For more information on Fusarium oxysporum as a plant pathogen, see Fusarium wilt.

Different strains of F. oxysporum have been used in the purpose of producing nanomaterials (especially Silver nanoparticles).

Formae speciales (special forms)[edit]

Patents relating to the management of Fusarium oxysporum[edit]

A number of recent patents specifically describe effective treatments of Fusarium oxysporum, reflecting its widespread importance as an agricultural pest.

  • US 5,614,188: two strains of Bacillus in a composition of chitin and lime used to fight Fusarium in the soil.
  • US 2004/136964 A1: Trichoderma asperellum mixed into container media (such as peat).
  • US 4,714,614: a strain of Pseudomonas putida in combination with an iron chelating agent (such as EDTA).
  • US 4988586: any of six types of bacteria that degrade fusaric acid, a toxin that damages plants and furthers infection.
  • US 6100449 and WO 1996/032007 A1: a small genomic region (I2C) conferring resistance in transgenic tomatoes.
  • US 2003/131376 A1: use of transgenic plants expressing enzymes capable of destroying Fusarium cell walls.
  • US 4006265: spraying of crops with hydrogen peroxide to reduce the effect of contamination by Fusarium toxins.
  • WO 2005/074687 A1: cure of infected plants by spraying with natamycin or other polyene antibiotics.

See also[edit]

References[edit]

  1. ^ Snyder, W.C. and Hansen, H.N. 1940. The species concept in Fusarium. Amer. J. Bot. 27:64-67.
  2. ^ Wollenweber, H.W. and Reinking, O.A. 1935. Die Fusarien, ihre Beschreibung, Schadwirkung und Bekampfung. P. Parey, Berlin. 365 pp.
  3. ^ Booth, C. 1971. The Genus Fusarium. Commonwealth Mycological Institute, Kew, Surrey, UK, 237 pp.
  4. ^ Nelson, P.E., Toussoun, T.A. and Marasas, W.F.O. 1983. Fusarium species: An illustrated manual for identification. Pennsylvania State University Press, University Park.
  5. ^ O'Donnell, K. and Cigelnik, E. 1997. Two divergent intragenomic rDNA ITS2 types within a monophyletic lineage of the fungus Fusarium are nonorthologous. Mol. Phylogenet. Evol. 7:103-116.
  6. ^ Waalwijk, C., De Koning, J.R.A., Baayen, R.P. and Gams, W. 1996. Discordant groupings of Fusarium spp. from section Elegans, Liseola and Dlaminia based on ribosomal ITS1 and ITS2 sequences. Mycologia 88:361-368.
  7. ^ Gordon, T.R. and Martyn, R.D. 1997. The evolutionary biology of Fusarium oxysporum. Annu. Rev. Phytopathol. 35:111-128.
  8. ^ Stoner, M.F. 1981. Ecology of Fusarium in noncultivated soils. Pages 276-286 in: Fusarium: Diseases, Biology, and Taxonomy. P.E. Nelson, T.A. Toussoun and R.J. Cook, eds. The Pennsylvania State University Press, University Park.
  9. ^ Rodriguez, A., Perestelo, F., Carnicero, A., Regalado, V., Perez, R., De la Fuente, G. and Falcon, M.A.1996. Degradation of natural lignins and lignocellulosic substrates by soil-inhabiting fungi imperfecti. FEMS Microbiol. Ecol. 21:213-219.
  10. ^ Sutherland, J.B., Pometto, A.L. III and Crawford, D.L. 1983. Lignocellulose degradation by Fusarium species. Can. J. Bot. 61:1194-1198.
  11. ^ Christakopoulos, P., Kekos, D., Macris, B.J., Claeyssens, M. and Bhat, M.K. 1995. Purification and mode of action of a low molecular mass endo-1,4-B-D-glucanase from Fusarium oxysporum. J. Biotechnol. 39:85-93.
  12. ^ Christakopoulos, P., Nerinckx, W., Kekos, D., Macris, B. and Claeyssens, M. 1996. Purification and characterization of two low molecular mass alkaline xylanases from Fusarium oxysporum F3. J. Biotechnol. 51:181-180.
  13. ^ Snyder, W.C. and Hansen, H.N. 1940. The species concept in Fusarium. Amer. J. Bot. 27:64-67.
  14. ^ Gordon, T.R., Okamoto, D. and Jacobson, D.J. 1989. Colonization of muskmelon and nonsusceptible crops by Fusarium oxysporum f. sp. melonis and other species of Fusarium. Phytopathology 79:1095-1100.
  15. ^ Katan, J. 1971. Symptomless carriers of the tomato Fusarium wilt pathogen. Phytopathology 61:1213-1217.
  16. ^ Larkin, R.P., Hopkins, D.L. and Martin, F.N. 1993. Effect of successive watermelon plantings on Fusarium oxysporum and other microorganisms in soils suppressive and conducive to fusarium wilt of watermelon. Phytopathology 83:1097-1105.
  17. ^ Lemanceau, P., Bakker, P.A.H.M., DeKogel, W.J., Alabouvette, C. and Schippers, B. 1993. Antagonistic effect of nonpathogenic Fusarium oxysporum Fo47 and pseudobactin 358 upon pathogen Fusarium oxysporum f. sp. dianthi. Appl. Environ. Microbiol. 59:74-82.
  18. ^ O’Donnell K, Kistler H C, Cigelnik E, Ploetz R C. 1998. Evolutionary origins of the fungus causing Panama disease of banana: Concordant evidence from nuclear and mitochondrial gene genealogies. PNAS (internet) (Cited 2014 September 15). 95(5): 2044-2049. Available from: http://www.pnas.org/content/95/5/2044.full
  19. ^ Fourie G, Steenkamp ET, Gordon TR, and Viljoen A. 2009. Relationships among the Fusarium oxysporum f. sp. cubense vegetative compatibility groups. Applied Environmental Microbiology (internet) (cited 2014 October 30). 75(14): 4770-4781. Available from: http://aem.asm.org/content/75/14/4770.full.pdf+html
  20. ^ Ploetz R. 2006. Fusarium Wilt of Banana is Caused by Several Pathogens Referred to as Fusarium oxysporum f. sp. cubense. Phytopathology (internet) (cited 2014 October 30). 96(6): 653-656. Available from: http://apsjournals.apsnet.org/doi/pdf/10.1094/PHYTO-96-0653
  21. ^ Appel DJ, and Gordon TR. 1994. Local and regional variation in populations of Fusarium oxysporum from agricultural field soils. Phytopathology (internet) (Cited 2014 October 30) 84:786-791. Available from: http://www.apsnet.org/publications/phytopathology/backissues/Documents/1994Articles/Phyto84n08_786.PDF
  22. ^ Teetor-Barsch, G.H. and Roberts, D.W. 1983. Entomogenous Fusarium species. Mycopathologia 84:3-16.
  23. ^ Nelson, P.E., Dignani, M.C. and Anaissie, E.J. 1994. Taxonomy, biology, and clinical aspects of Fusarium species. Clin. Microbiol. Rev. 7:479-504.
  24. ^ Kistler, H.C. 2001. Evolution of host specificity in Fusarium oxysporum. Pages 70-82 in: Fusarium: Paul E. Nelson Memorial Symposium. B.A. Summerell, J.F. Leslie, D. Backhouse, W.L. Bryden and L.W. Burgess, eds. The American Phytopathological Society, St. Paul, MN.

Bibliography[edit]

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Fusarium oxysporum f.sp. cyclaminis

Fusarium oxysporum f.sp. Cyclaminis is a fungal plant pathogen infecting cyclamens.

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Fusarium oxysporum f.sp. citri

Fusarium oxysporum f.sp. citri is a fungus which reproduces by cell fission. It is a well known plant pathogen infecting citruses.

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